Aware of the serious deficiencies revealed in the War with Spain and of the rapid technological changes taking place in the methods of warfare, the Army undertook comprehensive modernization of its weapons and equipment during the Root reform era. Development of high-velocity, low-trajectory, clip-loading rifles capable of delivering a high rate of sustained fire had already made obsolete the Krag-Jorgensen rifle that the Army had adopted in 1892. In 1903 the Regular Army began equipping its units with the improved bolt-action, magazine-type Springfield rifle with rod bayonet, which incorporated the latest changes in weapons technology. The campaigns of 1898 had shown that the standard rod bayonet was too flimsy, and starting in 1905 the Army replaced it with a one-pound knife bayonet with a sixteen-inch blade. In 1906 the addition of a greater propellant charge in ammunition and the adoption of a new 150-grain pointed bullet to replace the original 220-grain round-nosed bullet provided the Springfield with even higher muzzle velocity and enabled deeper penetration of the bullet. Combat at close quarters against the fierce charges of the Moros in the Philippines demonstrated the need for a less cumbersome hand arm that provided greater impact than the .38-caliber revolver. The Army found the answer in the recently developed .45-caliber Colt semi-automatic pistol, adopted in 1911.

Far more significant in revolutionizing the nature of twentieth-century warfare than these improved hand weapons was the rapid-firing machine gun. The manually operated machine gun--the Gatling gun--that the Army had adopted in 1866 was employed successfully in the Indian wars and the Spanish-American War. American inventors, including Hiram Maxim, John Browning, and Isaac N. Lewis, the last an officer in the Army's coast artillery, took a leading part in developing automatic machine guns in the years between the Civil War and World War I. Weapons based upon their designs were adopted by many of the world's armies. But not until fighting began in World War I was it generally realized what an important role the machine gun was to play in modern tactics. For procurement of machine guns between 1898 and 1916, Congress appropriated an annual average of only $150,000--barely enough to provide four weapons for each Regular regiment and a few for the National Guard. Although Congress in 1916 finally voted $12 million for machine gun procurement, the War Department held up expenditure of the funds until 1917, while a board tried to decide which type of weapon was best suited to the needs of the Army.

During this period, American field artillery developed a new generation of modern long-range, quick-firing guns and howitzers. These weapons possessed advanced on-carriage recoil systems and optical sights and used smokeless powder ammunition. The Army's new field gun, the Model 1902 3-inch gun, could fire over twenty rounds a minute, in contrast to the three rounds a minute of its black powder, ground recoil predecessor, the 3.2-inch gun that the Army had adopted in 1885. To facilitate delivery of long-range and indirect fire, artillery batteries were equipped with observing instruments, range finders, field telephones, and wire. To replace the black powder that had been the subject of widespread criticism in the War with Spain, both the Army and the Navy took steps to increase the domestic output of smokeless powder. By 1903 production was sufficient to supply most American artillery.

Experience gained in the Spanish-American War also brought some significant changes in the Army's coastal defense program. The hurriedly improvised measures taken during the war to protect Atlantic ports from possible attack by the Spanish fleet emphasized the need for modern seacoast defenses. Under the strategic concepts in vogue, construction and manning of these defenses were primarily an Army responsibility, since in wartime the naval fleet had to be kept intact, ready to seek out and destroy the enemy's fleet. On the basis of recommendations by the Endicott Board, convened in 1885, the Army already had begun an ambitious coastal defense construction program in the early 1890s, and in 1905 a new board headed by Secretary of War William Howard Taft made important revisions in this program with the goal of incorporating the latest techniques and devices. Added to the coastal defense arsenal were fixed, floating, and mobile torpedoes and submarine mines. At the same time, the Army's Ordnance Department tested 16-inch rifles for installation in the coastal defense fortifications, in keeping with the trend toward larger and larger guns to meet the challenge of naval weapons of ever-increasing size.

Of the many new inventions that came into widespread use in the early twentieth century in response to the productive capacity of the new industrial age, none was to have greater influence on military strategy, tactics, and organization than the internal combustion engine. It made possible the motor vehicle, which, like the railroad in the previous century, brought a revolution in military transportation, and the airplane and the tank, both of which would figure importantly in World War I.

The Army's use of motor vehicles had modest beginnings. In 1900 the Quartermaster General rejected a proposal for use of automobiles for military operations because he believed that insufficiently developed U.S. roadways precluded their widespread use. Even had he been an enthusiastic supporter of motor transport, the funds were not available for experimental automobiles or trucks. In 1906 his successor bought six automobiles, but the Treasury Department, ruling that he had exceeded his expenditure authority, charged them to his personal account. The next Quartermaster General was more successful. In 1907 he purchased twelve vehicles for testing. Initial tests indicated that they were not cost-effective, but attitudes were changing. In 1911, on the recommendation of the Inspector General, the Army purchased trucks for experimental purposes. The use of trucks and motorcycles in various tests and maneuvers showed the motor vehicle's potential, and by 1913 trucks were beginning to replace horses at depots. The Pershing Punitive Expedition to Mexico in 1916 provided the Army its first opportunity to use motor vehicles in a large-scale operation. To support the expedition, the War Department in March 1916 established two motor-truck companies, each consisting of 27 one-and-a- half-ton trucks. By July 1916 the Army had purchased 588 commercial trucks, 57 tank trucks, 10 machine-shop trucks, 6 wrecking trucks, 75 automobiles, 61 motorcycles, and 8 tractors for repairing roads. The use of these vehicles on the Mexican border was such a success that there were no longer any doubts that the truck would replace animal-drawn transportation. The experience gained from the use of motor transportation would be of tremendous value just months later when the United Sates entered World War I.

In the new field of military aviation, the Army failed to keep pace with early twentieth-century developments. Contributing to this delay were the reluctance of Congress to appropriate funds and resistance within the military bureaucracy to diversion of already limited resources to a method of warfare as yet unproved. The Army did not entirely neglect the new field; it had used balloons for observation in the Civil and Spanish-American Wars, and beginning in 1898 the War Department for several years subsidized Samuel P. Langley's experiments with power-propelled, heavier-than-air flying machines. In 1908, after some hesitation, the War Department made funds available to the Aeronautical Division of the Signal Corps (established a year earlier) for the purchase and testing of Wilbur and Orville Wright's airplane. Although the Army accepted this airplane in 1909, another two years passed before Congress appropriated a relatively modest sum--$125,000--for aeronautical purposes. Between 1908 and 1913, the United States spent only about $430,000 on military and naval aviation, whereas in the same period France and Germany each expended $22 million, Russia $12 million, and Belgium $2 million. Not until 1914 did Congress authorize establishment of a full-fledged Aviation Section in the Signal Corps. The few military airplanes available for service on the Mexican border in 1916 soon broke down, and the United States entered World War I far behind the other belligerents in aviation equipment, organization, and doctrine.